A conventional known stroller, referring to FIG. 11, has two front wheel rods 71, two rear wheel rods 72, a U-shaped bed frame 74 connected to the front and the rear wheels rods 71, 72, two front wheels 711 and two rear wheels 721, a main connecting base 81 of a collapsible structure for collapsing fixed on top of each of the front wheel rods 71, an auxiliary connecting base 82 pivoted to each of the rear wheel rods 72. The auxiliary base 82 is connected with a push handle 75 at an upper end. A shade frame 76 is provided, supporting sun shade 77 and pivoted to the bed frame 74. A bed 78 is provided, which is supported by the U-shaped bed frame 74.
The auxiliary base 82 of the collapsible structure 8 has a push block 83 movable in its interior and urged by a spring 84, forcing a projection 831 of the push block 83 to engage in a tubular hole 811 of the main base 81 to combine the main base 81 and the auxiliary base 82 together.
However, though the above conventional stroller is convenient for a baby to lie thereon and can be collapsed to a small size for storing, it is found to have disadvantages as follows.
1. When the push block 83 is pressed, the stroller will be in a position ready for collapsing, i.e. if a user should press the push block 83 by accident while a baby is still lying on the bed of the stroller, the stroller might be collapsed unwarily and result in injury of the baby.
2. When the stroller is collapsed, only the rear wheels touch the ground, i.e. the collapsed stroller has be leaned over a wall or otherwise put lying on the ground and thus might get dirty very easily.